Factors influencing accuracy of axillary sentinel lymph node frozen section for breast cancer

BackgroundIntraoperative sentinel lymph node (SLN) frozen section (FS) guides immediate axillary lymph node dissection in breast cancer patients.MethodsThe Oregon Health & Science University pathology database was searched for SLN FS From October 1999 to January 1, 2009. Slides of positive cases were reviewed and metastasis sizes measured.ResultsOf 416 cases, 129 were positive (31%) on permanent sections and immunohistochemistry, with 79 concordant and 50 false-negative FS. Accuracy was 88%, sensitivity 61%, and specificity 100%. FS accuracy for lobular carcinoma (76%) was lower than for invasive ductal carcinoma (88%) (P = .048). FS accuracy significantly differed by size of nodal tumor. For 49 cases of tumor ≤ 2 mm (isolated tumor cells plus micrometastases), the accuracy of FS was 18%; for 77 cases of >2-mm metastases, accuracy was 90% (P < .0001).ConclusionsFalse-negative FS were predominantly small nodal tumor deposits not sampled at FS. Although accuracy was lower, SLN FS is still beneficial in lobular carcinoma, but not ductal carcinoma in situ.